Webinar #8: Reporting vesicles and lesions – what to expect. USDA and state animal health officials presented what practitioners and producers need to know about the state and federal governments’ roles and responsibilities in investigating cases of vesicular disease. The National Animal Health Laboratory Network and the Plum Island Animal Disease Center described the samples, testing and timeline needed to rule out Foot and Mouth Disease during an investigation.
Swine SVV infection has occurred across the United States and Canada, and idiopathic vesicular disease has been reported globally from Europe to South America to Australia and New Zealand. Transmission of picornaviruses is generally very rapid and occurs in the cytoplasm of host cells. Clinical signs of SVV, when present, are indistinguishable from those of swine vesicular disease (SVD), vesicular stomatitis virus (VSV), vesicular exanthema of swine virus (VESV), and foot-and-mouth disease virus (FMDV), all more serious and economically devastating foreign animal diseases (FADs). Erosions, ulcerations, and vesicular lesions of the snout, oral mucosa, and distal limbs, especially around the coronary band, may be observed. Hoof sloughing and lameness can also occur, as well as more general symptoms of illness such as fever, lethargy, and anorexia.
Seneca Valley virus (SVV) is a small, non-enveloped picornavirus, unknown until 7557 when it was discovered incidentally as a cell culture contaminant. Only a single species, Senecavirus A, is currently classified in the Senecavirus genus of the family Picornaviridae, although sporadic serologically similar isolates have been identified in porcine samples spanning almost three decades. Naturally occurring antibodies against the virus have been detected in swine, cattle, mice, and a single human sample, though the virus is not known to cause disease in humans. Pathogenicity in swine remains unclear. Outbreaks of idiopathic vesicular disease have been linked to SVV in the absence of other identified etiologic agents and also during concurrent infection with porcine circovirus and porcine enterovirus. In contrast, the virus has also been identified in healthy pigs, and experimental infection has failed to produce clinical signs thus far.
There are two take home messages. First, they have defined the SVV incidence this summer as a “Type 8” status – national in scope with limited knowledge and tools. The details of a Type 8 status are in the AASV statement. That’s important to help put into context discussions about the effectiveness of local, specific responses like holding pigs from movement while waiting for them to stop shedding the virus.
Understanding the epidemiology of SVV and potential role of other species in virus transmission and origin, combined with continued development of rapid and specific diagnostics and elucidation of the link between viral infection and clinical disease in swine, will be crucial to our knowledge and ability to manage this newly discovered and little understood virus.
In its absence, the AASV Swine Health Committee was asked if they would help inform responses by reviewing the available information and decide the scope and distribution of SVV already in the . They also were asked to make recommendations about responses. That is what is attached.
The second is their repeated recommendation that pigs with illness or active SVV lesions should not be marketed until the lesions at least start to resolve. We can’t afford to have a packing plant shut down because of SVV being mistaken for FMD and stopping processing and commerce. At the same time, we can’t also become complacent and assume that active lesions are SVV, thus not alerting state or federal officials, whether on the farm or in the packing plant. Doing so puts pork producers, veterinarians and all of our industry at risk. Discussions are taking place with USDA and the packing companies about appropriate communications and responses about pigs that have had SVV, are healing, have had a FMD-negative test and are going to be presented to the market.
This document offers a starting point to address the investigation of foreign animal diseases—SVA
specifically—in a modern era where investigatory methods have not changed to meet the needs of
commerce in a fast‐paced and efficient pork industry. What used to be unusual (FAD investigations) has
become routine, resulting in a greater drain on limited resources (staffing, laboratory, financial). The
greatest challenge exists where the need to protect the industry from catastrophic disease events
intersects with commerce.
This isn’t “news”. It’s as it always has been. But there is heightened risk of complacency if we continue to find SVV after checking for FMD and that risk is unacceptable and avoidable.
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